Info on gear, conditioning, and preparation for hiking/climbing. Gear Classifieds
- Posts: 280
- Joined: Sun Aug 12, 2012 5:34 pm
- Location: Morrison, CO
Dave B wrote:mtn_nut wrote:I know that my ortovox s1+ has an inclinometer built in. I also use bca curved tube and I haven't had any issues with it.
I can't imagine that taking an avy beacon off to measure slope angle would be a super-great idea in avy terrain.
I think the crux of the issue is an ability to be able to tell what slopes are +/- safe (i.e. <30 degrees) and those that aren't. Beyond that, site-specific snow pack information is far more important than slope-angle.
The beacon has an elastic cord attached to it, so you don't have to remove the harness, and its still always attached to you.
Current Issue: TrailGroove Magazine
- Posts: 168
- Joined: Fri Sep 28, 2012 2:28 pm
- Location: Monument & Breck
TeamDino5280 wrote:If you are using USGS 7.5 minute quads the accuracy for vertical rise is 90% within half the contour interval. I think these have 40' contour lines which means that the change in elevation between contour lines should be 90% accurate within 20'. Now I think that you would need to take into account a 20' (+- 10%) error margin in the calculation.... total speculation on that one.
I think you are on to something here. Most slopes I am thinking of hiking, that warrant checking, are in the mid-twenty to mid-thirty degree range. And now that I think about it, it seems to be closer to 2 degrees off when measuring in the low to mid twenties...and closer to 3 degrees off when measuring in the upper twenties/low thirties. And just last week I measured a slope off the map at 38 degrees and the field check came in around 42 degrees. At the time I just wrote it off as a micro feature in the terrain. But now I see a pattern. Upper thirties being closer to a 4 degree inaccuracy makes sense. From now on I will use a 10 percent adjustment instead of a 2 to 3 degree adjustment. Thanks TeamDino!
Also, just wanted to mention a plus for an old school compass/inclinometer. The mirror. Ever get some debris in your eye when bushwhacking? And of course the possiblity of needing a signal mirror if lost/injured.
- Posts: 170
- Joined: Fri Jun 19, 2009 8:57 am
- Location: Green Mountain
I'm liking the discussion about determining slope angles from topo maps. This is something that I haven't messed around with much but would like to. Dancesatmoonrise, I tried your suggestion of printing a pdf topo at 235% zoom so that I could use my Lifelink card, but it was cumbersome because at that magnification, you can barely fit much of a map onto an 8.5x11 standard sheet of paper.
Another option is the AIARE field book, on the front inside cover it has a slope angle scale. The scale is set to 40' contour lines and you can use that to get a rough idea. Also if you don't want to carry the book you could just cut it out and carry it business card style. There are also slope rulers you can get for pre planning like this one http://www.maptools.com/products/SlopeRuler24.html all which work with the normal USGS quads.
- Posts: 274
- Joined: Sat Feb 13, 2010 3:08 pm
- Location: Golden, CO
Yet another option to estimate slope angle is to use your ski or trekking poles and some trigonometry. Arrange the poles in the shape of a right triangle with the slope being the hypotenuse. If the rise in the slope is equal to the run that's a 45 degree slope. If the rise is half the length of the run that's just under 30 and if the rise is twice the length the run, well, now you're over 60 degrees!
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